The present invention relates to a method of, and apparatus for, continuously applying grit particles to a continuous web. A roller is provided which is rotating about a substantially horizontal axis, and a (thin) layer of grit particles is provided on the upper part of the roller peripheral surface. The web is guided in a path which brings it into a receiving zone for receiving grit particles which have been carried up onto the upper part of the roller peripheral surface, to thereby grit the web. Such a method and apparatus are disclosed in FIGS. 8 to 10 of US Application Ser. No. 08/380,752, filed Jan. 31, 1995, for Waste Containment Landfill Enclosure and Components therefor, the subject matter of which is incorporated herein by reference (and to which corresponds GB 2 255 292A). By "continuous" is meant continuous in the normal manufacturing sense, although the webs normally have a finite length and the apparatus is not running all the time.
The apparatus shown in FIGS. 8 to 10 of GB 2 255 292A is relatively complex and expensive, and special care must be taken in order to control the even distribution of the grit particles on the upper part of the roller peripheral surface, which makes it difficult to increase the width of the machine in order to grit wider webs. The practical maximum width of this type of distribution mechanism was very roughly two meters; for product widths greater than this a plurality of such mechanisms would be required. A doctor blade is used to provide the final control of the grit particle distribution. A particular problem with a doctor blade is that a small amount of maladjustment causes a relatively large difference in the thickness of the grit particle layer, exacerbated in this case because the grit particles will cause fairly rapid wear of the blade. Wear of 0.01 or 0.1 mm can be significant. Such a problem exists with any arrangement for controlling the grit particle distribution by passing the grit particles through a predetermined gap of a width equal to the required thickness of grit particles on the web.
It is desirable to simplify the apparatus and make it less expensive. It is desirable to simplify the control of the distribution of the grit particles.